The present invention relates to a method for the production of packs of rolls of paper arranged in two or more rows.
Specifically, but not exclusively, the present invention is usefully applied for the production of packs of rolls of toilet paper arranged in five adjacent rows.
In the production of packs of rolls, in particular of toilet paper, machines are currently used which comprise elevator supporting surfaces, that can move vertically from a lower position in which they receive rolls of paper from roll production machines, to an upper position in which a sheet of plastic film, in particular made of polyethylene, is wrapped around the set of rolls to form the pack.
Said mobile supporting surfaces consist of two parts, mobile relative to one another, in such a way that, when there are three or more rows of rolls, as in the example illustrated in FIG. 1a, support for the central rows is guaranteed by the central part 1 of the supporting surface, whilst the outer part 2 of the supporting surface is withdrawn to the lower position and the horizontal flat folders 3, 4 are inserted under the rolls to join the two flaps of plastic film 5 together and so close the pack.
The central part 1 of the elevator surface is also withdrawn to the position in which new rolls are received, after the two ends of the horizontal flat folders 3, 4 make contact, during their forward movement towards the center of the structure, with the rolls in the central rows, supporting them in place of the above-mentioned central part of the elevator surface.
However, if the number of rows of rolls increases, as illustrated in the example in FIG. 1b, the problem of supporting one or more central rows while the horizontal flat folders move forwards towards the center of the pack arises again.
FIG. 1b shows how, unless a third mobile part is incorporated in the elevator supporting surface, at least the central row of rolls is left without any support when the mobile central part of the elevator is withdrawn towards the position in which the rolls are received, and so the stability of the central row becomes very precarious, since interaction with the adjacent rows as a result of possible interference between the diameters of the various rolls may not be sufficient.
The aim of the present invention is to overcome the above-mentioned disadvantage, at the same time avoiding any increase in machine structural complexity with the introduction of more mobile elements in the elevator supporting surface.
Another aim of the present invention is to propose a process for the automatic production of packs of rolls which is extremely rational and reliable.
Accordingly, the present invention fulfils the aforesaid aims with a method for the production of packs of rolls of paper in a packaging machine of the type comprising at least one supporting surface designed to lift ordered rows of rolls of paper from a first position, in which the rolls are received from roll production machines, to a second position, where a sheet of plastic film, in particular polyethylene, is stretched transversally to the direction of feed of the rolls. The rows of rolls are thrust against the sheet so that it is wrapped around the upper part and sides of the rows and the horizontal flat folders are activated to close the sheet flaps over the lower part of the rows. The supporting surface consists of two mobile parts, one at the center of the other, which can be activated separately for the return movement to the position in which the rolls are received, wherein the closing of the lower surface of the pack includes the steps of:
forward movement of the horizontal flat folders until the folders are close to the outer mobile part of the elevator supporting surface,
movement of the outer mobile part of the supporting surface to the position in which the rolls are received,
forward movement of the horizontal flat folders until they are close to the central mobile part of the elevator supporting surface,
downward movement of the central mobile part of the supporting surface, by an amount equal to the thickness of the horizontal flat folders,
stopping the central mobile part in the lowered position,
forward movement of the horizontal flat folders towards the plastic film sheet closing position,
movement of the central mobile part of the supporting surface towards the position in which the rolls of paper are received.
The central mobile part of the elevator surface stops in the intermediate position until the two ends of the flat folders make contact with the lower roll in the central row of rolls.
The two parts of which the elevator supporting surface consists may move at different speeds during the return step towards the position in which the rolls are received. In particular, the central part may, after an intermediate stop, move with a speed which allows it to reach the position in which the rolls are received practically simultaneously with the outer part of the supporting surface and thus restore surface continuity in the shortest possible time.
Closing of the polyethylene plastic film around the rows of rolls is completed, in a known way, with an operation for sealing the two end flaps of the sheet of polyethylene film with a sealing bar pressed against the overlapping flaps when the two flat folders are returned to the respective starting positions.
The features and advantages of the method disclosed are immediately evident from the above description, both relative to the possibility of continuing to use the machines currently in service, without changing the structural configuration, and as regards maintenance of a high level of hourly productivity associated with the method.